//: 字符串字面量.  包含双引号""的值成为字符串字面量.
"回到洪荒,去支配,去操纵"

//:  - 空字符串: 用""字面量
var a = ""
var b = "   "
//:  - 判断字符串是否为空
a.isEmpty
b.isEmpty

//: [>](@next)
